Some high power radio frequency (RF) amplifiers formed of bipolar transistors have problems with current collapse and sub-harmonics generation. The current collapse is caused by an asymmetrical circuit configuration and a non-uniform temperature distribution in the bipolar transistors. Current collapse is typically solved by a technique of dividing a large bipolar transistor into a plurality of amplifier cells with smaller bipolar transistors, and adding a plurality of resistors as ballasts to the bases and emitters of the smaller bipolar transistors in the amplifier cells. Although deep driving amplifiers at high power provides added efficiency, sub-harmonics are generated when bipolar transistors of the amplifiers are driven by a large RF signal. The sub-harmonic problem can not be disregarded because communication systems, such as global systems for mobile communication (GSM), typically have a sub-harmonic level lower than −35 dBm.